The present invention relates to an electronic circuit tester and more particularly to a portable circuit tester for testing standard electronic modules.
There is a constant demand for smaller electrical and electronic components, particularly in the aircraft and missile fields, as weight is of extreme importance. One concept of microelectronics which has been recently developed and which offers a great reduction in size and weight of electronic units is that of integrated circuitry which is formed on insulated bases such as glass, fused silica, or ceramic substrates. Integrated circuitry includes a number of active and passive components which are fabricated by one or more of a combination of several thin film deposition techniques onto a glass or ceramic substrate.
In order to reduce costs, expedite production, and provide a reliable electronic component, the Department of the Navy, as well as other military branches, have been engaged in a standard hardware program in which electronic plug-in modules have been developed which are capable of meeting various system requirements. One such plug-in module is shown in U.S. Pat. No. 3,243,660, entitled, "Electronic Module Assembly", which issued Mar. 29, 1966, to Leonard J. Yuska and David P. Zimmerman.
Both mechanical and electrical characteristics have been standardized in the Navy's Standard Electronic Modules Program. The basic SEM configuration is a single-span, single-thickness device having overall dimensions of 2.62 inches in width, 1.95 inches in height, and 0.290 inch in thickness. There are also provisions for multiple growth module increments for use in the development of modules of multiple span and thickness. Modules can be increased in span by increments of 3.00 inches and in thickness by increments of 0.300 inch. Mechanically, each module is comprised of a fin structure, ribs, contact pins, key pins and pin shields. The fin serves as the identification marking surface, extraction interface, and as a means for heat dissipation. Two holes are located in the module fin to aid in the removal of the module by use of an appropriate extraction tool. The ribs, at each end of the module span, aid in the alignment of the module in the card cage and assist in the proper mating of the module contacts and mounting structure connector. The ribs also provide a means for dissipating heat. The portion of each of the male contacts protruding from the header surface is configurately controlled to insure the proper engagement of the module and its interface mounting structure. The contacts are arranged in two rows of 20 contacts each on a 0.100-inch grid system to form module-connector increments. Each module increment may have a maximum of 40 contacts or a minimum of 20 contacts per module. Two keying pins serve to insure the proper mating of the module to its appropriate interface connector. Each module type is assigned a three-letter key code which identifies and establishes the configuration and rotational positions of the two uniquely configured keying pins. Modules having the same key code are both mechanically and electrically interchangeable. The pin shields function as a protective cover for the module contacts and a marking and identification surface.
In order that the basis for standardization could be effected, the standard electronic modules generally use standard digital logic levels and, also, standardized power supply voltages of .+-.5 Vdc, .+-.12 Vdc, .+-.15 Vdc and .+-.25 Vdc are used with a power supply voltage tolerance of .+-.10 percent. Additionally, SEM power supply, circuit ground, frame ground, and signal lines have been assigned to specific contact pins on the module connector. These requirements have been established to permit the use of commonly used power and ground bussing techniques, thereby enabling the simplification of backpanel wiring techniques.
The use of Standard Electronic Modules by the Navy has had many beneficial results such as lower design and production costs, reduced logistics cost and increased Fleet readiness by the reduction of overall inventory, and improved reliability through standardization controls invoked on the module specifications.
System level repair now requires that a technician or engineer who thoroughly understands the system under repair to trouble shoot the system with the aid of a maintenance manual and standard or special laboratory instruments. This is a time consuming method. Some of the later electronic systems contain a system self-check program. This program aids the repair by isolating the system fault to a group of modules. By replacing the suspect modules one at a time, the system self-check program can find the bad module. The disadvantage is that the self-check program is time consuming and may need to be run a great number of times before the bad module is detected.